Conventional golf balls can be divided into two general classes: solid and wound. Solid golf balls include one-piece, two-piece (i.e., single layer core and single layer cover), and multi-layer (i.e., solid core of one or more layers and/or a cover of one or more layers) golf balls. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material, and a cover.
Examples of golf ball materials range from rubber materials, such as balata, styrene butadiene, polybutadiene, or polyisoprene, to thermoplastic or thermoset resins such as ionomers, polyolefins, polyamides, polyesters, polyurethanes, polyureas and/or polyurethane/polyurea hybrids, and blends thereof. Typically, outer layers are formed about the spherical outer surface of an innermost golf ball layer via compression molding, casting, or injection molding.
From the perspective of a golf ball manufacturer, it is desirable to have materials exhibiting a wide range of properties, such as compression, coefficient of restitution (CoR), spin, and “feel” because this enables the manufacturer to make and sell golf balls suited to differing levels of ability and/or preferences. In this regard, the industry has previously explored incorporating nano-sized sturctures such as nanofibers, nanotubes, and nanoparticles in golf ball compositions in order to alter or adjust properties such as specific gravity, modulus, and/or tensile strength.
However, golf ball manufacturers have observed that nanostructures are difficult to disperse throughout golf ball polymer compositions and form agglomerations. See, e.g., Sullivan et al., U.S. Pat. No. 8,758,167 (“Sullivan '167”). Agglomeration of nanostructures within a polymeric matrix can interfere with molding of the composition into a golf ball component as well as negatively impact the resulting characteristics of the finished golf ball.
Sullivan '167 proposes improving nanostructure dispersibility and avoiding agglomeration by “substantially orienting” nanostructures within the golf ball composition. Sullivan '167 specifies orienting at least 10%, at least 25%, at least 50%, at least 75%, at least 90% or more of the nanostructures of each set or cluster of nanostructures relative to a designated axis, plane, surface or three dimensional space. Sullivan '167 further specifies that the orienting can be substantially parallel, substantially perpendicular, or at a selected angle (for example, about 15°, 30°, 45°, or 60°). Moreover, each set of nanostructures can include splayed or angularly-gathered nanostructures (for example, star patterns or hexagonal groupings) as well as substantially aligned populations of nanostructures and as described in Whiteford et al., U.S. Pat. No. 7,662,313.
Unfortunately, substantially orienting nanostructures in golf ball compositions increases the margin for error on the assembly line and raises manufacturing costs. Accordingly, there remains a need for golf balls that include nanostructures which disperse within a golf ball composition without orienting. Such improved golf balls, if meanwhile producible within existing manufacturing processes and which can improve a wide range of golf ball properties would be particularly useful, efficient and cost effective. The current golf balls of the invention and methods for making same advantageously address and solve these needs.